Motion systems for loading tips

ABSTRACT

Embodiments of lab automation workstations are disclosed in which the pod that performs pipetting operations is integrated with pipette tip-loading functionality. To generate the necessary tip-loading force, a dual drive system is used that is symmetric about the Y-axis to allow for offset or partial tip box loads by dynamically centering the drive force (e.g., the tip-loading force) over the reaction load. This minimizes the need for oversized linear motion components while still allowing for the generation of high tip-loading forces needed to properly load a large number of pipette tips simultaneously.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a U.S. National Stage application ofPCT/US2018/012959, filed Jan. 9, 2018, which claims the benefit ofpriority to U.S. Provisional Application No. 62/446,124, filed Jan. 13,2017, the disclosures of which are hereby incorporated by reference intheir entireties. To the extent appropriate, a claim of priority is madeto each of the above-disclosed applications.

FIELD

Methods and systems disclosed herein relate generally to lab automationworkstations and related devices for the precise handling of liquids.More specifically, the various designs and techniques disclosed hereincan be used with lab automation workstations in order to betterintegrate the loading of pipette tips into the lab workflow, resultingin a more-convenient and more-efficient loading of pipette tips.

BACKGROUND

Lab automation workstations, which are sometimes referred to as liquidhandling robots or pipette workstations, are frequently used in theautomation of chemical and biochemical laboratories to facilitate theprecise handling of liquids. These robots often use a motorized pipetteor syringe to dispense a selected volume of liquid (e.g., a reagent,sample, etc.) into designated containers.

More complex lab automation workstations may have design configurationsthat allow them to mimic the operations of humans and reproducepipetting procedures used by humans in order to perform liquidtransfers. For example, such workstations may be able to preciselymanipulate the position of the pipette dispensers and containers inorder to perform advanced operations such as the mixing of liquids. Someof these workstations may have an arm that allows for precise, 3-axismovement of the pipette dispensers.

The various components of the lab automation workstation may be managedby control software, either on a connected computer or integrated intothe system itself. The control software may allow the user to customizethe liquid handling procedures and transfer volumes, as well asmanipulate the various components of the workstation to perform thedesired liquid handling procedures.

Some lab automation workstations may be configured for multiple pipettedispensers and the simultaneous use of multiple pipette tips. However,the simultaneous loading of multiple pipette tips for use by theseworkstations may require the use of a relatively large amount of forcethat has to be appropriately applied to the pipette tips. Thus, a labautomation workstation may have to be specifically designed to properlyapply that force. Embodiments of the invention solve these and otherproblems individually and collectively.

BRIEF SUMMARY

Embodiments of lab automation workstations are disclosed in which thepod that performs pipetting operations with pipette tips is integratedwith pipette tip-loading functionality. In order to integrate thepipette tip-loading functionality, the components for two or more drivesin the Z-axis can be included in the pod in order to generate thedesired tip-loading forces at the appropriate locations. In someembodiments, a dual drive system that is symmetric about the Y-axis canbe used. The system allows for offset or partial tip box loads bydynamically centering the drive force (e.g., the tip-loading force) overthe reaction load. Such a system also minimizes the need for oversizedlinear motion components while still allowing for the generation of hightip-loading forces needed to properly load a large number of pipettetips simultaneously. Furthermore, the use of two identical sets ofcomponents in the dual drive system allows the components to bedownsized as each set of components for a drive is only required togenerate about half of the total tip-loading force needed.

In some embodiments, a motion system is disclosed that comprises: afirst drive screw; a second drive screw parallel to the first drivescrew, the first drive screw independently rotatable relative to thesecond drive screw; a platform including a first location, the platformconfigured to engage the first drive screw and the second drive screw,wherein activation of the first drive screw and the second drive screwdisplaces the platform, and wherein the first location is offset fromthe first drive screw and from the second drive screw; a position sensorconfigured to measure a first position of the platform at the firstlocation; and a first force sensor configured to detect a first forcefrom the first drive screw.

In certain embodiments, the motion system may further comprise a secondforce sensor configured to detect a second force from the second drivescrew. In certain embodiments, the platform further includes a secondlocation offset from the first drive screw, from the second drive screw,and from the first location, and wherein the position sensor is furtherconfigured to measure a second position of the platform at the secondlocation. In certain embodiments, the platform is subdivided into afirst area and a diagonally opposed second area by a centerline and amidline, the centerline intersecting the centers of the first drivescrew and the second drive screw and the midline perpendicular to thecenterline through the midpoint of the centerline, and wherein the firstlocation is disposed in the first area and the second location isdisposed in the second area. In certain embodiments, the position sensorincludes a first linear encoder adjacent the first location and a secondlinear encoder adjacent the second location. In certain embodiments, themotion system further comprises a motor operatively coupled to the firstdrive screw, wherein the first force sensor comprises a winding of themotor.

In some embodiments, a pipette workstation is disclosed that comprises adeck configured to support a plurality of pipette tips; a pipettor headengaged to a first drive screw and a second drive screw, the pipettorhead disposed above the deck and movable with respect to the deck inresponse to a torque applied to the first drive screw and a torqueapplied to the second drive screw, wherein, when the plurality ofpipette tips is present, the plurality of pipette tips produce aninsertion force on the pipettor head; a first force sensor coupled tothe first drive screw and configured to detect a first value of theinsertion force; and a controller configured to adjust the torque of thefirst drive screw in response to the detected first value of theinsertion force.

In certain embodiments, the pipette workstation may further comprise asecond force sensor coupled to the second drive screw and configured todetect a second value of the insertion force. In certain embodiments,the pipette workstation may further comprise a first linear encoder anda second linear encoder offset from the first linear encoder, the firstlinear encoder configured to measure a first position of the pipettorhead and the second linear encoder configured to measure a secondposition of the pipettor head, wherein the controller is furtherconfigured to adjust the torque of the second drive screw in response tothe first position and the second position. In certain embodiments, thecontroller is configured to apply a torque to the first drive screw toproduce a predetermined first value of the insertion force. In certainembodiments, the controller is configured to apply a torque to thesecond drive screw to maintain the measured second position level withthe measured first position. In certain embodiments, the controller isconfigured to apply a torque to the second drive screw to produce apredetermined second value of the insertion force. In certainembodiments, the pipettor head is subdivided into a first area and adiagonally opposed second area by a centerline and a midline, thecenterline intersecting the centers of the first drive screw and thesecond drive screw and the midline perpendicular to the centerlinethrough the midpoint of the centerline, and wherein the first positionis measured in the first area and the second position is measured in thesecond area. In certain embodiments, the pipettor head includes aplurality of mandrels each configured to engage a pipette tip, andwherein, when the plurality of mandrels engage the plurality of pipettetips, fewer than all of the plurality of mandrels are engaged.

In some embodiments, a method is disclosed of driving a pipettor headsubject to an off-center load, the method comprising: moving a pipettorhead to engage an off-center load, the pipettor head engaging a firstdrive screw and a second drive screw independently rotatable relative tothe first drive screw; measuring a first position of the pipettor headat a first location and a second position of the pipettor head at asecond location; measuring a first force transmitted from the off-centerload by the first drive screw; calculating a first torque and a secondtorque based upon a set of parameters including the first force, thefirst position, the second position, and a representation of theoff-center load; and applying the first torque to the first drive screwand the second torque to the second drive screw.

In certain embodiments, the first torque is greater than the secondtorque. In certain embodiments, the method further comprises measuring asecond force transmitted from the load by the second drive screw. Incertain embodiments, the set of parameters includes the first force andtwo or more of the second force, the first position, the secondposition, and the representation of the off-center load. In certainembodiments, the first torque and the second torque produce apredetermined force at the off-center load. In certain embodiments, thefirst torque and the second torque levels the pipettor head whileengaged with the off-center load.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described in conjunction with the appendedfigures:

FIG. 1A shows a perspective view of example embodiments of a labautomation workstation that utilize an external tip loader.

FIG. 1B shows a perspective view of a pod used in example embodiments ofa lab automation workstation.

FIG. 1C shows a perspective view of mandrels used in example embodimentsof a lab automation workstation.

FIG. 1D shows a perspective view of example embodiments of a pipette tiptray.

FIG. 2 shows a bottom perspective view of the internal components of apod used in example embodiments of a lab automation workstation.

FIG. 3 shows a top perspective view of the internal components of a podused in example embodiments of a lab automation workstation.

FIG. 4A shows a side perspective view of the internal components of apod used in example embodiments of a lab automation workstation.

FIG. 4B shows a top-down view of the internal components of a pod usedin example embodiments of a lab automation workstation.

FIG. 5 shows a top-down view of an interface plate used in exampleembodiments of a lab automation workstation.

FIG. 6A shows a flowchart depicting the loading of a partial set, orselective quantity, of tips in accordance with example embodiments of alab automation workstation.

FIG. 6B shows a side perspective view of the loading of a partial set oftips in accordance with example embodiments of a lab automationworkstation.

FIG. 7 shows a block diagram of a system according to an exampleembodiment of a lab automation workstation.

In the appended figures, similar components and/or features can have thesame reference label. Further, various components of the same type canbe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

The ensuing description provides preferred exemplary embodiments only,and is not intended to limit the scope, applicability or configurationof the disclosure. Rather, the ensuing description of the preferredexemplary embodiments will provide those skilled in the art with anenabling description for implementing various embodiments. It isunderstood that various changes may be made in the function andarrangement of elements without departing from the spirit and scope asset forth in the appended claims.

Overview and Context

Some lab automation workstations may be configured for multiple pipettedispensers and the simultaneous use of multiple pipette tips. However,the simultaneous loading of multiple pipette tips for use by theseworkstations may require the use of a relatively large amount of forcethat has to be appropriately applied to the pipette tips. Thus, a labautomation workstation may have to be specifically designed to properlyapply that force.

It should be noted that FIGS. 1A-1D show example embodiments of a labautomation workstation that utilize an external tip loader to supply thelarge amounts of force necessary needed to load pipette tips for use bythe workstation. However, such embodiments of the workstation utilizingan external tip loader are provided for exemplary purposes and are notintended to be limiting. Instead, the external tip loader is describedin order to better facilitate understanding and provide context for thisdisclosure.

With regards to the figures, FIG. 1A shows an example embodiment of alab automation workstation 100, which may include any combination of thevarious systems or components shown. For example, the lab automationworkstation 100 may include one or more (or none) each of an arm 102, apod 104, a tip tray 106, and an external tip loading station 108. Anoverview of these various components of the lab automation workstation100 is provided below.

In some embodiments, the lab automation workstation 100 may include anarm 102. In some of such embodiments, the arm 102 may be movable alongone or more axes. For example, the arm 102 may be laterally slideablealong the length of the lab automation workstation 100. In someembodiments, the lab automation workstation 100 may include a pod 104that is mechanically coupled to the arm 102. As shown in the figure, thepod 104 may have an elongate housing in the vertical axis that is heldupright by the arm 102. The bottom of the pod 104, which is shown inmore detail in FIG. 1B, may be configured to interface and/or connect toone or more pipette tips. In some of such embodiments, the pod 104 maybe moveable along the arm 102 in one or more axes. For example, as shownin the figure the pod 104 may be laterally slideable along the length ofthe arm 102. Furthermore, in some embodiments, the pod 104 may bevertically slideable relative to the arm such that the bottom of the pod104 can be positioned higher or lower. Accordingly, the bottom of thepod 104 may be re-positioned with precise, 3-axis movement by adjustinga combination of: the height of the pod 104 relative to the arm 102(e.g., the Z-axis), the lateral position of the pod 104 along the arm102 (e.g., the Y-axis), and the lateral position of the arm 102 alongthe length of the lab automation workstation 100 (e.g., the X-axis).

In some embodiments, the pod 104 may be a multichannel pod which isconfigured for interfacing with, and connecting to, multiple pipettetips that can be simultaneously used to perform pipetting operations. Insome embodiments, the pod 104 may contain various components that allowfor various pipetting and fluid-handling operations to be performedusing attached pipette tips.

In some embodiments, the lab automation workstation 100 may beconfigured to allow the bottom of the pod 104 to be re-positioned over atip tray 106, as shown in the figure. In some of such embodiments, thetip tray 106 may rest on top of the external tip loading station 108.The tip tray 106 may contain one or more pipette tips usable forhandling liquids. These pipette tips often come sterilized and are heldin rows and/or columns of the tip tray 106. Pipette tips in varioussizes or shapes, and the tip tray 106 used to hold them may also come indifferent sizes or shapes in order to accommodate varying numbers andconfigurations of pipette tips. A non-limiting example of a tip tray 106is shown in additional detail in FIG. 1D. Some common configurations ofthe tip tray 106 include designs for holding 96 or 384 pipette tips.This allows for pipetting liquid into 96-well or 384-well plates, with apipette tip for each well.

In some embodiments, the lab automation workstation 100 is configured tore-position the bottom of the pod 104 over the top of the pipette tipsheld in the tip tray 106. In some of such embodiments, the external tiploading station 108 may be configured to provide an upward force againstthe bottom of the pipette tips held in the tip tray 106, which pushesthe pipette tips upwards towards the bottom of the pod 104. In someembodiments, the pod 104 may have a set of mandrels configured toreceive the top of the pipette tips. Non-limiting examples of themandrels are shown in FIG. 1B and FIG. 1C. The top of the pipette tipsmay be configured to attach to the mandrels via a friction fit. Thus,pushing the pipette tips in the tip tray 106 upwards towards themandrels located at the bottom of the pod 104 (which is positioned overthe pipette tips) may force the pipette tips onto the mandrels andprovide an air-tight connection between the pipette tips and themandrels.

However, it should be noted that since each pipette tip may beconfigured to attach to a mandrel via friction fit, the amount of forcenecessary to push that pipette tip onto the mandrel, and create anair-tight connection between that pipette tip and the mandrel, can berelatively large. Furthermore, since a tip tray 106 may have a largenumber of pipette tips (e.g., as many as 96 or 384—or even greater), theamount of force necessary to simultaneously push all of those pipettetips onto the mandrels to produce air-tight connections can be enormous.In some embodiments, simultaneously loading 384 pipette tips onto themandrels may require 500 or more pounds of force.

FIG. 1B shows an example embodiment of the pod 104 of the lab automationworkstation 100. In some embodiments, the pod 104 may include mandrels110 at the bottom of the pod 104. Each mandrel may be configured toattach to a pipette tip, and each mandrel may have an elongate channel(not shown) that spans the vertical length of the mandrel. This elongatechannel may allow each mandrel to facilitate the performance ofpipetting operations on an attached pipette head. For example, theelongate channel may be used to create varying degrees of pressurewithin an attached pipette tip, allowing for liquid to be sucked into,or expelled from, the bottom of that pipette tip.

In some embodiments, the pod 104 may include one or more grippers 112.The grippers 112 may be used to carry objects or reposition themrelative to the pod 104. For example, in some embodiments the grippers112 may be used on a tip tray 106 in order to ensure that the tops ofthe pipette tips in the tip tray 106 are aligned with each of themandrels 110. In some embodiments, the grippers 112 may be used to grasponto a tip tray 106 to allow re-positioning of the tip tray 106, such asplacing the tip tray 106 on top of an external tip loading station 108for the loading of pipette tips onto the pod 104.

In some embodiments, the pod 104 may include a head 114 at the bottom ofthe pod 104. In some of such embodiments, the mandrels 110 may reside onthe head 114.

FIG. 1C shows an example embodiments of the mandrels 110. As shown inthe figure, the mandrels 110 are in a 8×12 configuration, for a total of96 mandrels. Thus, the mandrels 110 can be simultaneously attached to 96pipette tips. In some embodiments, each mandrel may be generallycylindrical with an elongate channel that spans the vertical length ofthe mandrel. This elongate channel may allow each mandrel to facilitatethe performance of pipetting operations on an attached pipette head. Forexample, the elongate channel may be used to create varying degrees ofpressure within an attached pipette tip, allowing for liquid to besucked into, or expelled from, the bottom of that pipette tip. In someembodiments, each mandrel may be tapered towards the bottom end or havefeatures at the bottom end that facilitate an air-tight friction fitwith the top of a corresponding pipette tip.

FIG. 1D shows an example embodiment of a tip tray 106. As shown in thefigure, the pipette tips are held upright in the tip tray 106 in a 16×24configuration, for a total of 384 pipette tips. These pipette tips wouldbe used with a corresponding set of mandrels 110 having the same 16×24configuration to allow pipetting operations to be performed with up to384 pipette tips. As previously mentioned, in order to load as many as384 pipette tips onto the mandrels 110, a large amount of force may berequired—as much as 500 or more lbs of force.

This required force can be generated through the use of an external tiploading station, such as the external tip loading station 108 shown inFIG. 1A, which pushes the pipette tips upwards to be seated onto themandrels 110 of the pod 104. Thus, the external tip loading station 108may generate and provide a substantial amount of force in the verticalaxis.

However, in some embodiments, it may be desirable for the lab automationworkstation to do without the external tip loading station 108.Depending on the exact method of operation of an external tip loadingstation 108, it may take up a large amount of available deck space.Furthermore, the use of an external tip loading station 108 may requirethat the pod 104 be re-positioned over the external tip loading station108 in order to load the pipette tips—greatly limiting where the pipettetips may be loaded. This increases processing times for any workflowperformed by the lab automation workstation 100, as time is repeatedlyspent on moving pipette tips to and from the external tip loadingstation 108 and re-positioning the pod 104 over the external tip loadingstation 108 in order to perform tip loading.

Integrated Drive System

In some embodiments, it may be desirable to combine the functionalitiesof the external tip loading station 108 and the pod 104. Morespecifically, it is desirable to add the force-providing functionalityof the external tip loading station 108 to the pod 104 and remove theneed for the external tip loading station 108 altogether.

In particular, integrating the tip-loading functionality into the pod104 would allow pipette tips to be loaded anywhere on the deck of theworkstation. This would result in less shuffling of labware during theworkflow (e.g., needing to move a full tip tray on top of an externaltip loading station any time tip loading is to be performed), whichimproves the efficiency of the workflow and reduces the total operatingtime. Furthermore, integrating the tip-loading functionality into thepod 104 also improves the flexibility of the workspace by freeing upadditional space within the lab automation workstation for labware orother equipment that can be used.

However, there may be various challenges associated with integrating thetip-loading functionality into the pod 104. As previously mentioned, onesuch challenge is that simultaneously loading the pipette tips from afull tip tray 106 onto the pod 104 may require a large amount of force.Without an external tip loading station 108, this force has to beprovided by the pod 104 itself. In embodiments for which the pod 104does not have its own tip-loading capability, the pod 104 may be mainlyconfigured to contain the components necessary to aspirate smallquantities of fluid. The addition of the tip-loading capability to thepod 104, which may require the pod 104 to generate downward force inexcess of 500 lbs needed for tip-loading, means that numerous additionalcomponents have to be added to the pod 104.

In some embodiments, the addition of extra components to the pod 104 maynot be an issue and the dimensions of the pod 104 may be expanded inorder to accommodate the extra components for generating the requiredtip-loading force. However, in other embodiments, the dimensions of thepod 104 may be constrained for some reason. For example, the height ofthe elongate pod 104 may be constrained. A taller pod 104 may beundesirable for both aesthetic and functional purposes, as it limits thespaces that the lab automation workstation 100 may fit in.

One way to address the space issue is to reduce the force that isrequired for tip-loading. A reduction in the required tip-loading forceresults in smaller vertical loads and moments produced on the componentsof the pod 104, allowing for smaller components to be used within thepod 104 that can still withstand those vertical loads. This would allowa pod with tip-loading capability to retain similar dimensions, or eventhe same pre-defined dimensional footprint, as a pod without tip-loadingcapability. The maximum tip-loading force needed depends on theinsertion force required to seat each pipette tip onto a mandrel of thepod 104. There are four primary ways of reducing this insertion force:(1) using overshot/co-molded pipette tips; (2) using thin-wall pipettetips; (3) using mandrels with an o-ring or made of elastomer; and (4)optimizing mandrel geometry and material.

However, these methods of reducing the required tip-loading force maynot always be feasible. For instance, relying on overshot/co-moldedpipette tips requires the use of special pipette tips which may notalways be available and are likely to be more costly than more standardpipette tips. O-ring mandrels may be sensitive to tolerance stack-upsand require frequent replacement of the o-rings; passive elastomermandrels may similarly require frequent maintenance. Finally, optimizingmandrel geometries and materies may not reduce the insertion forceenough to serve as a single solution towards reducing the tip-loadingforce needed. Several of these alternative methods for reducing therequired tip-loading force are also likely to affect the positionalrepeatability of loading the tips.

Thus, since it is difficult to reduce the required tip-loading force, abetter solution for dealing with the space issue may instead be to addthe extra force-generating components to the pod 104 without having tosignificantly expand the dimensions of the pod 104 (while keeping inmind that the components themselves cannot be downsized since thetip-loading force cannot be reliably reduced). In some embodiments, thecomponents for generating the tip-loading force within the pod 104 maybe collectively referred to as the drive system.

One way to add a drive system to the pod 104 without having tosignificantly increase the dimensions of the pod 104 is through the useof lead screws or ball screws. This disclosure makes reference to leadscrews for ease and simplicity, but any suitable alternatives forproviding precise linear motion (to a mounting plate, as described inFIG. 2 ) are contemplated, including ball screws, pistons, linearactuators, and so forth.

In some embodiments, the pod 104 may have one or more “drive elements”,such as a first drive element or a second drive element. A drive elementmay be any device or component capable of providing precise linearmotion, including lead screws, ball screws, pistons, linear actuators,just to give a few examples.

In some embodiments, the pod 104 may have a drive system that includesone or more lead screws that span the vertical axis of the pod 104. Thelead screws could be driven by one or more motors in order to push themandrels down onto the pipette tips with the necessary force needed fortip-loading.

For example, in some embodiments the pod 104 may have a single leadscrew that spans the vertical axis of the pod 104. In some of suchembodiments, the single lead screw may be located in the center of boththe X-axis and Y-axis of the pod 104. In other words, the lead screw mayrun from the top of the pod 104 towards the bottom of the pod 104through the center of the pod 104, and it may provide a symmetricalload. In some of such embodiments, this lead screw may be able toprovide upwards of 500 lbs of force. This example demonstrates acentered drive system that is located vertically over the geometriccenter of the pod 104, which minimizes the moments that are generatedwithin the pod 104. However, in this example, the pod 104 also containsthe components to perform the various pipetting operations through themandrels 110 at the bottom of the pod 104. These components may includepumps for each of the mandrels, which run down the center of the pod 104since the mandrels 110 are also centered at the bottom of the pod 104.These pumps may also be referred to as “plungers” or “pistons”. Thus,for a pod 104 configured with pipetting hardware for a set of 384mandrels, they may be as many as 384 separate pumps. Thus, in order fora single lead screw to run down the center of the pod 104, it would haveto go through the center of those pumps which is possible, but difficultto accommodate without increasing the dimensions of the pod 104.

In other alternative embodiments, the pod 104 may instead have a singlelead screw that is off-center or runs along one of the sides of the pod104. Such an offset drive system may allow for a more vertically-compactpod 104 than a centered drive system, with the lead screw still beingable to provide upwards of 500 lbs of force. However, using an offsetdrive system, there would be a cantilevered load that is notsymmetrical. In other words, with an offset drive system, the ability toapply a force at the geometric center of the entire pod 104 whilemaintaining horizontal stability of the interface plane (where the pod104 connects to the pipette tips) becomes difficult. If the system isnot rigid enough, the load applied to the pipette tips will have agradient across the tip tray 106, with the end effect of unevenly loadedpipette tips (e.g., some pipette tips will be seated more securely, orfurther onto the mandrels, than others). This can be an issue because anair-tight connection with each of the pipette tips is desired.Furthermore, it is also very important for tips to be loaded to the sameconsistent height. If they are not, which could occur with an offsetdrive system, some of the tips will reach the bottom of the pipette wellwhile others do not. This may impact the capability for performinglow-volume pipetting operations and the overall coefficient of variationfor pipetting because some of the tips (e.g., the tips that do not reachthe bottom of the pipette well) could end up sucking up air bubblesinstead of the desired reagent. In order to counteract the momentsapplied to the system, the pod 104 and its components are strengthenedto be able to resist rocking about the load center. Increasing the sizeof all of the linear motion components within the pod 104 to resist thebending moments would allow for offset loads while still maintaining theorientation of the interface plate. The resulting pod that is used withan offset drive system ends up becoming much larger in both the X-axisand Y-axis, as well as being heavier, than a comparable pod with acentered drive system capable of delivering the same loading force. Inthe scenario where the pod 104 is constrained to a pre-defineddimensional footprint, it may be possible but difficult to fit theupsized, strengthened components within the pod 104 in order toaccommodate the offset drive system.

Thus, it is possible but may be difficult to use a single lead screw inthe pod 104 without increasing the dimensions of the pod 104, regardlessof whether a centered or offset drive system is used. In otherembodiments, two or more lead screws may be simultaneously used in orderto provide the required tip-loading force at a geometric center of theentire pod 104 without needing any lead screws to run through the centerof the pod 104. Thus, any number of lead screws of two or more can beused. For example, four lead screws could be used, with a lead screw oneach side of the pod 104 or at each corner of the pod 104. The use ofadditional lead screws may be beneficial for load-matching purposes, asdisclosed later in this application. However, it should be noted thatthe use of too many lead screws may take up additional space within thepod 104 and require a larger pod 104 to accommodate those lead screws.The following example embodiments depicted in the figures utilized twolead screws, a configuration which is intended to be non-limiting andprovided merely for the purposes of facilitating understanding of theoperation of the drive system.

With regards to the figures, FIGS. 2-5 are directed towards exampleembodiments of a pod utilizing two lead screws, with each lead screwlocated on an opposing side of the pod and running parallel to theZ-axis of the pod. Both lead screws may be configured to deliver forceused in tip-loading by pushing downwards on both sides, which allows forthe added benefit of the load being evenly split between the two leadscrews when the load is centered between the two lead screws.

FIG. 2 shows a bottom perspective view of the internals of a podutilizing two lead screws according to one example embodiment.

More specifically, the pod 200 may include a first lead screw 202 and asecond lead screw 204 that span the vertical axis of the pod 200 and areon opposing sides of the pod 200. At the bottom end of the pod 200 is amounting plate 206, an interface plate 208, and a center piece 210 whichcarries the mandrels. Accordingly, the center piece 210 interfaces withthe pumps (and other components for pipetting operations) held in thecenter of the pod 200, with the resulting pipetting operations takingplace at the bottom of the pod 200 at the center piece 210.

As shown in the figure, in some embodiments, both the first lead screw202 and the second lead screw 204 may be anchored to the top and thebottom of the pod 200. In some embodiments, the first lead screw 202 andthe second lead screw 204 run through the mounting plate 206, as well asthe interface plate 208. The bottom ends of the first lead screw 202 andthe second lead screw 204 may be affixed to the interface plate 208; asseen in the figure, the first lead screw 202 terminates at the bottomend of the pod 200 and the second lead screw 204 terminates at thebottom end of the pod 200. The lengths of the lead screws may be of anysuitable lengths. In some embodiments, the lead screws can be about aslong as the vertical length of the pod 200.

In some embodiments, the mounting plate 206 and the center piece 210 maymove up and down relative to the lead screws, while the interface plate208 remains anchored to the bottom ends of the lead screws. In some ofsuch embodiments, the mounting plate 206 and the center piece 210 maymove up and down relative to the lead screws as a result of the leadscrews being turned clockwise or counterclockwise. In some embodiments,the interface plate 208 is part of the drive system and helps supply thenecessary tip-loading force. As the interface plate 208 is positionedover tray of pipette tips, the turning of the lead screws may result inthe mounting plate 206 and the center piece 210 (containing themandrels) to be driven downwards towards the pipette tips. As themandrels are pushed downwards with the necessary tip-loading force, themandrels become attached to the pipette tips via friction fit.

FIG. 3 shows a top perspective view of the internals of a pod utilizingtwo lead screws according to one example embodiment.

More specifically, FIG. 3 illustrates how the lead screws, such as thefirst lead screw 202 and the second lead screw 204, may be turned invarious embodiments of the pod 200. It is contemplated that any methodand configuration may be used for turning the lead screws, and not onlythrough the use of motors mechanically coupled to the lead screws.Furthermore, there may be any number of motors that are mechanicallycoupled to any number of lead screws.

As shown in the figure, each individual lead screw is mechanicallycoupled to an independent motor. For instance, the top of the first leadscrew 202 may be mechanically coupled to a first motor 302. In someembodiments, the first motor 302 may be within an enclosure andmechanically coupled to the first lead screw 202 by a pulley and belt,both of which may also be housed within the enclosure. The operation ofthe first motor 302 may be used to turn the first lead screw 202clockwise and counter-clockwise. The top of the second lead screw 204may be mechanically coupled to a second motor 304. In some embodiments,the second motor 304 may also be within an enclosure and mechanicallycoupled to the second lead screw 204 by a pulley and belt, both of whichmay also be housed within that enclosure. The operation of the secondmotor 304 may be used to turn the second lead screw 204 clockwise andcounter-clockwise. As in the previous figure, both lead screws may spanthe vertical dimensions of the pod 200 and may be anchored at both thetop of the pod 200 and the bottom of the pod 200.

Thus, in various embodiments, each lead screw used in the drive systemmay be mechanically coupled to an independent motor that drives it. Thisconfiguration may also provide numerous advantages towards allowing forthe loading of a partial rack of pipette tips, as opposed to the loadingof all the pipette tips in a tip tray. In a typical scenario where afull tip tray is loaded, a symmetrical downward force can used. Forinstance, the workstation may re-position the bottom of the pod to becentered over the full tip tray. During tip-loading, a reaction force isproduced in the Z-axis that is centered at both the X-axis and Y-axis ofthe bottom of the pod 104. Thus, any drive system capable of deliveringa symmetrical downward tip-loading force can be used to pick up all ofthe pipette tips in the tray because the downward tip-loading force willbe aligned with the reaction force.

However, when it comes to the partial loading of pipette tips, whereonly some of the pipette tips in the tip tray are loaded rather than theentire tray, the bottom of the pod may not be perfectly centered overthe tip tray or the array of tips remaining in the tip tray. Forexample, in order to load pipette tips on the right side of the tiptray, those pipette tips may be aligned with the left side of the bottomof the pod. This would allow for the pod to pick up only those pipettetips on the right side of the tip tray and not any of the other pipettetips in the tray (e.g., the pipette tips on the left side of the tiptray). In this scenario, the reaction force produced by the tip traywould not be centered on the bottom of the pod, but rather positionedtowards the left side of the bottom of the pod. In general, during apartial load of the tip tray, the total reaction force may be decreasedbut may be moved off-center in one or more of the X-axis and Y-axis ofthe pod. In other words, the reaction force could be produced towards aside or corner of the bottom of the pod, rather than at the center.

This creates an offset load (an uneven load on the pod), which makes itdifficult to apply the right amount of tip-loading force to the pipettetips or to keep the pod parallel to the array of tips. If not enoughforce is being applied to those specific pipette tips, or if the poddoes not remain parallel to the array of tips, the pipette tips mayattach to the mandrels but may not be seated well on the mandrels. Theconnection may leak air and those pipette tips will not handle pipettingoperations well. If too much force is being applied to those specificpipette tips, the pipette tips may be crushed.

As will be described later in this application in regards to FIG. 5 ,independently driving the lead screws can be used to deal with thisproblem, so that the pod 200 can be used to load a full tray of pipettetips, a partial tray of pipette tips, or even a single pipette tip. Thepod 200 may have one or more rails or guides, such as rail 306 (theremay be a corresponding rail on the other side of pod 200 that is notviewable in FIG. 3 ), that guides the movement of the mounting plate 206and prevents the mounting plate 206 from tilting too much—as may be thecase if the independently-driven lead screws turn out of sync or if oneof the lead screws is turned too much. If the mounting plate 206 tiltstoo much, the pod 200 may jam and further movement of the mounting plate206 may not be possible. Thus, the rails or guides may hold the mountingplate 206 level. Furthermore, the control exerted over the motors mayalso ensure that the lead screws are not turning out of line with eachother, which may cause the mounting plate 206 to tilt.

FIG. 4A shows a side perspective view of the internals of a podutilizing two lead screws according to one example embodiment.

FIG. 4B shows a top-down view of the internals of a pod utilizing twolead screws according to one example embodiment.

With regards to both FIG. 4A and FIG. 4B, many previously-describedcomponents of the pod can be seen in relation to each other.

For example, the first lead screw 202 (e.g., an example of a first driveelement) can be seen operatively and mechanically coupled to a firstmotor 302 via a timing pulley and belt 402 and anchored at the top ofthe pod. The first lead screw 202 also runs through the mounting plate206 and is anchored at the bottom of the pod at the interface plate 208.Similarly, the second lead screw 204 (e.g., an example of a second driveelement) can be seen operatively and mechanically coupled to a secondmotor 304 via a timing pulley and belt 404 and anchored at the top ofthe pod. The second lead screw 204 also runs through the mounting plate206 and is anchored at the bottom of the pod at the interface plate 208.In some embodiments, there may be a first force sensor configured todetect a first force coming from the first drive element. In someembodiments, the first force sensor may be a component of the firstmotor 302. In some embodiments, the first force sensor may include awinding of the first motor 302. In some embodiments, there may be asecond force sensor configured to detect a second force coming from thesecond drive element. In some embodiments, the second force sensor maybe a component of the second motor 304. In some embodiments, the secondforce sensor may include a winding of the second motor 304.

The mounting plate 206 (e.g., an example of a platform or a pipettorhead) moves up and down along the first lead screw 202 and the secondlead screw 204, as well as the rails 306 and 308 which help prevent themounting plate 206 from tilting as it moves up and down. In someembodiments, the mounting plate 206 or platform may include a firstlocation. In some embodiments, the mounting plate 206 or platform may beconfigured to engage the first drive element and the second driveelement, and the activation of the first drive element and the seconddrive element may displace the mounting plate 206 or platform. In someembodiments, this first location on the mounting plate 206 or platformmay be offset from the first drive element and from the second driveelement. In some embodiments, the mounting plate 206 or platform mayfurther include a second location offset from the first drive element,from the second drive element, and from the first location. In someembodiments, the mounting plate 206 or platform may be subdivided into afirst area and a diagonally opposed second area by a centerline and amidline. The centerline may intersect the centers of the first driveelement and the second drive element and the midline perpendicular tothe centerline through the midpoint of the centerline. In certainembodiments, the first location of the platform is disposed in the firstarea and the second location of the platform is disposed in the secondarea.

In some embodiments, the mounting plate 206 or pipettor head may beengaged to a first drive screw and a second drive screw (such as thefirst lead screw 202 and the second lead screw 204). The pipettor headmay be disposed above a deck (such as the center piece 210 shown in FIG.2 or the mandrels 110) may move up and down relative to the lead screws,while the interface plate 208 remains anchored to the bottom ends of thelead screws. In some of such embodiments, the mounting plate 206 may bemovable with respect to the deck in response to a torque applied to thefirst drive screw and a torque applied to the second drive screw. When aplurality of pipette tips is present, the plurality of pipette tips mayproduce an insertion force on the pipettor head. In some embodiments,the deck may be configured to support a plurality of pipette tips. Insome embodiments, there may be a first force sensor coupled to the firstdrive screw and configured to detect a first value of the insertionforce produced by the plurality of the pipette tips. For example, thefirst force sensor could be a winding in the first motor that isoperatively coupled to the first drive screw. In some embodiments, theremay be a second force sensor coupled to the second drive screw andconfigured to detect a second value of the insertion force produced bythe plurality of the pipette tips. For example, the second force sensorcould be a winding in the second motor that is operatively coupled tothe second drive screw.

In some embodiments, there may be a controller (for example, the centralcontroller 700 shown in FIG. 7 ) configured to adjust the torque of thefirst drive screw in response to the detected first value of theinsertion force detected by the first force sensor. The controller mayalso be configured to adjust the torque of the second drive screw inresponse to the detected second value of the insertion force detected bythe second force sensor. In some embodiments, the controller may beconfigured to apply a torque to the first drive screw to produce apredetermined first value of the insertion force to be detected by thefirst force sensor.

In some embodiments, there may be a first encoder strip 412 (e.g., anexample of a first linear encoder) that runs parallel along the lengthof the first lead screw 202. In some embodiments, there may also be asecond encoder strip 414 (e.g., an example of a second linear encoder)that runs along the length of the second lead screw 204. In someembodiments, there may be a first encoder head 422 (e.g., an example ofa first position sensor) on the mounting plate 206 (e.g., at the firstlocation of the platform) and a second encoder head 424 (e.g., anexample of a second position sensor) on the mounting plate 206 (e.g., atthe second location of the platform). The encoder strips and the encoderheads can be used to measure the position of the mounting plate 206along the lead screws. This information can be used for feedbackpurposes in controlling the motors, which were previously mentioned tobe independently driven. In some embodiments, a first position sensormay be configured to measure a first position of the platform at thefirst location. In some embodiments, a second position sensor may beconfigured to measure a second position of the platform at the secondlocation. In some embodiments, the first position sensor may include afirst linear encoder adjacent the first location. In some embodiments,the second position sensor may include a second linear encoder adjacentthe second location. As will be described in regards to FIG. 5 ,independently driving the motors and the lead screws, as well ascollecting feedback information useful towards controlling thoseindependently driven motors, can allow for the pod to perform partialloading of pipette tips from a tray while dealing with offset loads.

In some embodiments, there may be a first encoder strip 412 (e.g., afirst linear encoder) and a second encoder strip 414 (e.g., a secondlinear encoder). The second linear encoder may be offset from the firstlinear encoder. The first linear encoder may configured to measure afirst position of the mounting plate 206 (e.g., pipettor head) and thesecond linear encoder may be configured to measure a second position ofthe pipettor head. In some embodiments, the controller (such as thecentral controller 700 shown in FIG. 7 ) may be configured to adjust thetorque of the second drive screw in response to the first position andthe second position of the pipettor head measured by the first andsecond linear incoders. In some embodiments, the controller may beconfigured to apply a torque to the second drive screw to produce apredetermined second value of the insertion force to maintain themeasured second position level with the measured first position. In someembodiments, the controller may be configured to apply a torque to thesecond drive screw to produce a predetermined second value of theinsertion force. In some embodiments, the two offset encoder strips(first encoder strip 412 and second encoder strip 414) may be useful formaintaining the levelness of the pod relative to the array of tips whenthe pod is pushing against an offset force created by a partial array oftips in the tip tray.

As previously mentioned, in some embodiments the mounting plate 206 orpipettor head may be subdivided into a first area and a diagonallyopposed second area by a centerline and a midline. The centerline mayintersect the centers of the first drive screw and the second drivescrew and the midline perpendicular to the centerline through themidpoint of the centerline. The first position may be measured using afirst position sensor in the first area and the second position may bemeasured using a second position sensor in the second area. In someembodiments, the pipettor head may include a plurality of mandrels eachconfigured to engage a pipette tip. In some cases, when the plurality ofmandrels engage the plurality of pipette tips, fewer than all of theplurality of mandrels are engaged. This advantageously allows flexibleuse of the pipettor head for a limited set of liquid transfers whileconserving pipette tips.

FIG. 5 shows a top-down view of the interface plate. More specifically,FIG. 5 shows the positionings of various components in relation to thecenter of the interface plate.

As previously mentioned, the use of multiple lead screws, such as leadscrews 202 and 204, can allow for the partial loading of pipette tips.In other words, in a tip tray containing 384 pipette tips, the labautomation workstation may be able to control the pod to pick up only asubset of those pipette tips (e.g., any number from one tip to the fullamount of 384 tips).

In general, the pod may be able to only pick up a certain arrangement oftips from the tray at one time. This may typically involve using aregion of the mandrels that opposes the region of the tip tray that thetips are being picked up from. For example, in order to pick up therightmost column of tips in a full tip tray, the left side of themandrels would be lowered onto those tips. To pick up the topmost row oftips in a full tip tray, the bottom side of the mandrels would belowered onto those tips. To pick up tips off the top right corner of thetray, the bottom left corner of the mandrels could be lowered onto thosetips.

More complex arrangements of tips may be picked up through a combinationof multiple tip-loading procedures. For example, an “L” shapedarrangement of tips that includes the leftmost column and bottommost rowof tips could be picked up using a combination of two tip-loadingprocedures. In some embodiments, the lab automation workstation can havean imager, camera, or sensor to detect and determine the positions ofavailable tips held in the tip tray. In some of such embodiments, theimager, camera, or sensor may be integrated with the pod. In someembodiments, the control software for the lab automation workstation maybe able to automatically determine the necessary combination oftip-loading procedures to pick up a certain arrangement of pipette tipsand then automatically perform that combination of tip-loadingprocedures.

As previously described, in these examples that involve the partialloading of pipette tips, since the pod is not being centered directlyover the tip tray (as would be the case with a full loading of tips)there is an uneven load on the pod. In other words, the reaction forceassociated with only loading the rightmost column of tips in a tip trayholding 384 tips would be offset from the center. However, themagnitude, location, and distribution of that uneven load can bedetermined. In some embodiments, the magnitude, location, anddistribution of that uneven load can be mathematically modelled andknown in advance. For example, just by knowing that only the rightmostcolumn of tips is to be loaded onto the mandrels, the magnitude anddistribution of the load can be determined.

Since the screws are being driven using independent motors, more forcecan be supplied through one lead screw than the other by adjusting thetorque provided by each of the motors. The lead screw convers the rotarymotor torque into a force applied to the pod. Different, but precise,amounts of force can be delivered through each lead screw in a mannerthat counteracts the uneven load on the pod, so that the downwardtip-loading force being applied matches the load while the mandrels arekept level. The end result is that the pod (and the mandrels) can bekept level with the right amount of tip-loading force being delivered tothe pipette tips. Otherwise, if the mandrels are not kept level, thepods will pick up tips at an angle and have the possibility of jamming.Or if the force is too low, the pipette tips may not seat well on themandrels and will leak air, or the pipette tips may be loaded toinconsistent heights relative to the mandrels. Or if the force is toohigh, the pipette tips will be crushed by the force.

As previously mentioned, this concept could be extended to multipledrives for the Z-Axis (e.g., a third lead screw). Adding a third drive,for example, could help to normalize forces about an additional axis(e.g., the X axis in addition to the Y axis). Thus, in some embodiments,the pod may utilize three lead screws with each lead screw mechanicallycoupled to an independent motor. For example, the three lead screws maybe positioned in a triangular configuration and span the vertical axisof the pod as opposed to the figures shown, in which two lead screws areon opposing sides of the pod.

However, in order to be able to adjust the force provided by the leadscrews to counteract the uneven load while keeping the mandrels level,the lab automation workstation must be able to determine the force beingprovided by each lead screw, as well as determine whether the mandrelsare being kept level (or if they are tilted, and the degree of tilt).Various methods and embodiments for determining the forces provided bythe lead screws and whether the mandrels are level are described below.

In some embodiments, the lab automation workstation may be able tomeasure the force provided by the lead screws by measuring the currentsin the motors that are coupled to the lead screws. Those currents may becorrelated to a force through a mathematical model of the drive system.

In order to determine whether the mandrels are being kept at the sameheight, a good proxy is to determine whether the mounting plate is beingkept level since the mandrels will move higher or lower along with themounting plate. In some embodiments, the lab automation workstation maybe able to determine the corner positions of the mounting plate alongthe vertical axis, which can be used to determine whether the mountingplate has a tilt in either the X or Y planes. In some of suchembodiments, the lab automation workstation may have linear encoderstrips that run alongside the lead screws. These strips may includemagnetic domains or optical markings or other detectable properties thatvary along the length of each linear encoder strip. The mounting platemay have encoder heads that correspond to the encoder strips runningalongside the lead screws, such that the lab automation workstation candetermine how far along the lead screw the corner positions (where theencoder heads are) of the mounting plate are. By measuring the tilt ofthe mounting plate, if the lab automation workstation senses a tilt inthe mounting plate occuring despite knowing the load distribution inadvance, the lab automation workstation can infer that one of the leadscrews is delivering too much force and can adjust the motors inresponse.

With reference to the figures, the linear encoder magnetic strips may beencoder strips 412 and 414 as seen in FIG. 4A that run alongside thelead screws. However, the encoder strips, as well as the encoder heads(such as encoder heads 422 and 424 as seen in FIG. 4B) on the mountingplate that correspond to them, may not necessarily be on the lead screwsthemselves but may instead be offset from them. The offset can be betterseen in FIG. 5 . Relative to the center of the interface plate, theencoder head 422 (and the corresponding encoder strip 412) has both a Xoffset and a Y offset from the center of the interface plate. Similarly,the encoder head 424 (and the corresponding encoder strip 412) also hasboth a X offset and a Y offset from the center of the interface plate.With two linear encoders situated on opposite corners (front right andrear left) the mandrels can be kept level and both motors can be kept insync.

By positioning both encoder heads with X and Y offsets on opposing sidesof the interface plate, only two encoder heads are needed to determinethe tilt of the mounting plate in both the X and Y planes. This is animprovement over having both encoder heads on the same Y coordinate,which would result in potential tilt of the mandrels about the X axiswithout a means of detection.

In contrast, if a single encoder were used, it may be difficult toproperly sync the motors and the ability to dynamically level the podwould not exist, as it would not be possible to know how level themandrels are. It would be possible for one motor to drive harder andfaster than the other and induce excessive wear and binding situations,causing the pod to jam.

FIG. 6A shows a flowchart depicting the loading of a partial set of tipsin accordance with example embodiments of a lab automation workstation.

In the previous figures, embodiments of a pod with integratedtip-loading functionality was shown utilizing two lead screws (e.g., adual drive in the Z-axis). This dual drive Z-axis setup was described asutilizing two feedback systems—one regarding the force being deliveredthrough the screws and one regarding the tilt of the mounting plate. Insome embodiments, the dual drive Z-axis setup may utilize these twofeedback systems which operate independently, but exist within a singlemicroprocessor. Both feedback systems are started or stoppedsimultaneously and managed by a common motion system which synchronizethe status of each motor. This abstracts the dual drive system in amanner such that the instrument software treats the dual drive as asingle motor. For example, if one of the dual motors encounters aproblem which results in the motor stopping, the common motion systemmay automatically stop the other motor before reporting the error to theinstrument software.

At block 602, the lab automation workstation may determine the tips tobe loaded onto the mandrels of the pod. This may be in response to aninput from a user, such as if the user makes a selection in the controlsoftware regarding which tips in the tip tray to be loaded. Thus, anynumber ranging from a single tip to all of the tips in the tray may beselected to be loaded. In some embodiments, the lab automationworkstation may include an imager, camera, or sensor that can detectwhich tips in the tip tray are available to be loaded.

As previously mentioned, in some scenarios the arrangement of tips to beloaded may be more complex and require multiple loadings to beperformed. In such a scenario, the lab automation workstation may beable to automatically determine the necessary combination of loadingprocedures to be performed and execute them, which may involveperforming blocks 604, 606, 608, and 610 multiple times—one for eachloading procedure in the combination.

At block 604, the lab automation workstation may home the dual drivesystem and determine its state. Prior to the system being homed, thestate of the dual drive system (e.g., the positions of the motors) arenot known. For proper operation the motors must be homed to a knownlocation such as a physical hard stop. In some embodiments, both motorsare driven simultaneously in the direction of the hard stop with alimited force until that force limit is reached for a configured amountof time. Once the hard stops are found for each motor, their respectiveencoder positions are set to the home position. The time element isparticularly important to prevent falsely finding the home location. Insome embodiments, before starting the search for the hard stops, it maybe necessary to ensure that the two motors are aligned enough to movewithout binding. This is accomplished by driving each motor in oppositedirections, recording each position, then reversing the direction ofeach motor, again recording the positions, then moving each motor to theaverage of the found positions. The common motion system automaticallymanages this process as part of homing.

At block 606, the lab automation workstation may determine an operatingmode to use for controlling the delivery of the tip-loading forcedepending on the tips to be loaded. In some embodiments, the labautomation workstation may be able to automatically determine theoperating mode to use for the tips to be loaded without needing humaninput. Various operating modes are disclosed below:

One operating mode is a push move, in which the motors are driven untila desired output force is obtained. In applications such as loading afull tray of tips, an even force distribution is required to ensure alltips are loaded. Simply driving the mounting plate to a certain positionmay not be adequate since various factors such as levelness of the tiptray and flexing of the chassis or deck plates can cause uneven forceson each side of the tip tray. Driving each motor to a constant forceallows both motors to move until a configured force is obtained for adefined amount of time. Force can be measured by a force gauge(transducers or strain gauges, for example) or by measuring currentgoing to the motors. To perform a push move, both motors in the dualdrive system are given a target force which is converted to a motorcurrent value. Both motors are started simultaneously and follow theirrespective trajectories until the motor current limit is reached for thespecified amount of time. When both motors reach the limit or the targetposition is reached, the push move is complete. When the mechanicalcomponents flex (the chassis or deck plates, for example) this has acompensatory effect that distributes the force more evenly over thesurface of the tip tray. For the partial loading of tip trays, the forceneeded from each motor may be different. Various distributions of forcesmay be applicable. For example, the system may calculate the geometriccenter of the load based on a model of the force required for each tipand the geometric distribution of pipette tips with respect to the pod.The system may then project the calculate geometric center onto thecenterline connecting the lead screws and calculate torques for each ofthe lead screws, where at least a portion of each torque is inverselyrelated to the distance between the respective lead screw and theprojected geometric center.

Another operating mode is a position-based feedback move, in which bothmotors are driven in a closed-loop fashion using the linear encoders forfeedback until the motors are in a desired position. A typicalposition-based feedback move for a single motor utilizes a trajectorygenerator to set the desired position of the motor over time, an encoderto compare the actual position to the desired position, and a controlloop to generate the control variable which is the input to the motordrive system. In the dual drive system, each motor has its owntrajectory generator which plots a trajectory to the same targetposition. It is possible for the starting positions to be different ifthe two motors are not perfectly aligned at the start of a move. In someembodiments, there may be encoder feedback shared between motors, suchthat feedback from both encoders is utilized in amulti-input/multi-output (MIMO) PID control loop. The rationale is thatone motor may get ahead of the other motor causing the dual drive pod totilt, which further results in the binding of the linear guidecomponents. Including encoder feedback from both motors in the controlof each motor will detect the tilt and equalize the positions of themotors.

Another operating mode is a one-sided push move, in which one motor isdriven until a desired output force for that motor is obtained, whilethe other motor is tracked using position. For example, if the pod isloading a column of tips on the left side and no other tips, the leftmotor will be programmed to move with a specific force. The targetposition of the right motor will be determined by the relative distancethe left encoder has moved from its starting position. In other words,if the left motor reaches the target force after moving N encoder countsfrom its starting position, the target position of the right motor willbe N encoder counts past the start position of the right motor.

Another operating mode is an asymmetric push move, in which a push moveis performed but the motors are driven until two different desiredoutput forces are obtained between the motors. This may be useful forthe partial loading of tip trays, since the desired output forces arecalculated to intentionally distribute the force unevenly. Thedistribution of the force will be based on the location and quantity ofthe tips being loaded.

At block 608, the lab automation workstation may begin loading tips bydriving the lead screws in order to move the mounting plate downwards inorder to attach the mandrels to the pipette tips, in accordance with theselected operating mode.

At block 610, the lab automation workstation may monitor the feedbacksystems until the desired positions or forces associated with the motorsare attained.

FIG. 6B shows a side perspective view of the loading of a partial set oftips in accordance with example embodiments of a lab automationworkstation.

More specifically, the figure illustrates a pod 104 and a tip tray 106containing 384 pipette tips in a 16×24 configuration. The pod 104 hasbeen tasked with picking up 4 rows and 16 columns of pipette tips fromthe tip tray 106. Accordingly, the pod 104 is not positioned directlyover the center of the tip tray 106. Instead, the pod 104 is positionedat an offset from the center, such that only the 4×16 array of tips iscontacted by the pod 104 and picked up. The actual implementation ofloading this partial set of tips from the tip tray 106 can be understoodby referencing the above description associated with FIG. 6A.

Alternative Embodiments

In some embodiments, the pod may utilize an offset loading scheme with asingle-sided drive system. For example, there could be a single leadscrew off-center within the pod. The linear motion components may needto be increased in size in order to deal with the moments created byoffset reaction forces.

In some embodiments, the pod may utilize a drive system that is centeredwithin the pod, with zero or minimal offset of the Z-drive relative tothe geometric center of the pod. For example, there could be a singlelead screw centered within the pod. This may require the pod to have agreater vertical height to avoid conflict with dispense mechanisms inthe center region of the pod.

In some embodiments, there may be a single motor coupled to two screwswithin the pod. This system would have a single motor that uses either aserpentine belt arrangement or a redundant set of drive pulleys to drivetwo driven pulleys mounted to the screws. There may be a single encoderused to track position. With this arrangement, belt tension, initialtiming (or clocking) or components, and tolerances become much morecritical. The ability to drive one screw more than the other tocompensate for any unevenness or tilt is lost.

In some embodiments, there may be two motors and two screws, but only asingle encoder. If there is any difference in drag between the twodrives it would cause a potential binding situation as the system cannotdetect the levelness of the mandrels and would not know the trueposition of each drive relative to the read point.

FIG. 7 shows a block diagram of a system according to an exampleembodiment of a lab automation workstation.

In some embodiments, there may be a number of drive elements, such as afirst drive element 702 and a second drive element 704. There may bemore drive elements as well, up to a Nth drive element 706. Each driveelement may be any device or component capable of providing preciselinear motion and downward force for tip-loading. Examples of driveelements include lead screws, ball screws, pistons, linear actuators,and so forth. Each drive element may interface with a central controller700. The central controller 700 may send signals or instructions tocontrol and operate the various drive elements. As previously described,these drive elements may be in the pod of the workstation. In someembodiments, there may be a platform including a first location, theplatform configured to engage the first drive element 702 and the seconddrive element 704, wherein activation of the first drive element 702 andthe second drive element 704 displaces the platform. In someembodiments, the first location may be offset from the first driveelement 702 and from the second drive element 704.

There may also be one or more force sensors 712 in communication withthe central controller 700. The force sensors 712 may be configured tomeasure the force being applied through the various drive elements. Insome embodiments, there may be a force sensor corresponding to eachdrive element. For example, there may be a first force sensor configuredto detect a first force from the first drive element 702, and there maybe a second force sensor configured to detect a second force from thesecond drive element 704. In some embodiments, the force sensors may beintegrated with the drive elements or the components that cause thedrive elements to move. The force sensors 712 may communicate with thecentral controller 700 in order to report the forces associated with thedifferent drive elements, such that the central controller 700 isprovided feedback.

There may also be one or more position sensors 714 in communication withthe central controller 700. In some embodiments, the position sensors714 may be configured to measure various positions associated with theplatform. For example, a there may be a first position sensor configuredto measure a first position of the platform at a first location, as wellas a second position sensor configured to measure a second position ofthe platform at a second location. As described herein, these positionsensors 714 may be used to detect the tilt associated with the platform.In some embodiments, the position sensors 714 may be magnetic linearencoder strips corresponding to an encoder head; the position of theplatform may be determined magnetically based on the position of theencoder head along the corresponding encoder strip.

There may be an imager 708 in communication with the central controller700. In some embodiments, the imager 708 may relay information about theposition of pipettes within a tip tray to the central controller 700.That information can be used by the central controller 700 in order todetermine various approaches and algorithms for loading those pipettetips.

There may also be pump components 710 in communication with the centralcontroller 700. The central controller 700 may issue signals or commandsto the pump components 710 in order to perform pipetting operations withthe pipettes that are in fluid communication with those pump components710. In some embodiments, the pump components 710 are within the pod,along with the platform and the various drive elements.

The various devices or components for pod movement 716 may also be incommunication with the central controller 700. In some embodiments, thecentral controller 700 may issue signals or commands to those componentsfor pod movement 716 in order to move the pod around in the X, Y, and/orZ axis. Thus, the central controller 700 may control re-positioning ofthe pod in order to perform tip-loading and pipetting operations.

It should be understood that the present invention as described abovecan be implemented in the form of control logic using computer softwarein a modular or integrated manner. Based on the disclosure and teachingsprovided herein, a person of ordinary skill in the art will know andappreciate other ways and/or methods to implement the present inventionusing hardware and a combination of hardware and software

Any of the software components or functions described in thisapplication, may be implemented as software code to be executed by aprocessor using any suitable computer language such as, for example,Java, C++ or Perl using, for example, conventional or object-orientedtechniques. The software code may be stored as a series of instructions,or commands on a computer readable medium, such as a random accessmemory (RAM), a read only memory (ROM), a magnetic medium such as ahard-drive or a floppy disk, or an optical medium such as a CD-ROM. Anysuch computer readable medium may reside on or within a singlecomputational apparatus, and may be present on or within differentcomputational apparatuses within a system or network.

The above description is illustrative and is not restrictive. Manyvariations of the invention will become apparent to those skilled in theart upon review of the disclosure. The scope of the invention should,therefore, be determined not with reference to the above description,but instead should be determined with reference to the pending claimsalong with their full scope or equivalents.

One or more features from any embodiment may be combined with one ormore features of any other embodiment without departing from the scopeof the invention.

A recitation of “a”, “an” or “the” is intended to mean “one or more”unless specifically indicated to the contrary.

What is claimed is:
 1. A method of driving a pipettor head, the methodcomprising: a) moving a pipettor head using a first drive screw and asecond drive screw, the first drive screw and the second drive screwbeing independently rotatable relative to one another; b) measuring afirst position of the pipettor head at a first location using a firstposition sensor and a second position of the pipettor head at a secondlocation using a second position sensor, wherein the first location isalong the first drive screw and the second location is along the seconddrive screw; c) measuring a first force applied to the pipettor head bya plurality of pipette tips in response to a first insertion forceapplied by the first drive screw, wherein the first force is unevenlydistributed to the pipettor head; d) calculating a first torque and asecond torque based upon a set of parameters including: the first force,the first position, and the second position; and e) applying the firsttorque to the first drive screw and the second torque to the seconddrive screw to counteract the uneven distribution of the first force. 2.The method of claim 1, wherein the first torque is greater than thesecond torque.
 3. The method of claim 1, further comprising measuring asecond force transmitted applied to the pipettor head by the pluralityof pipette tips in response to a second insertion force applied by thesecond drive screw.
 4. The method of claim 3, wherein the set ofparameters are: the first insertion force and two or more of the secondinsertion force, the first position, the second position, the firstforce and the second force.
 5. The method of claim 1, wherein the firsttorque and the second torque produce a predetermined force at theplurality of pipette tips.
 6. The method of claim 1, wherein the firsttorque and the second torque level the pipettor head while the firstforce is applied to the pipettor head.
 7. A motion system comprising: afirst drive screw; a second drive screw independently rotatable relativeto the first drive screw; a pipettor head engaging the first drive screwand the second drive screw; a processor; and a computer readable mediumstoring data instructions for driving a pipettor head, wherein the datainstructions, when executed by the processor, cause the motion systemto: move the pipettor head using the first and the second drive screw;measure a first position of the pipettor head at a first location usinga first position sensor and a second position of the pipettor head at asecond location using a second position sensor, wherein the firstlocation is along the first drive screw and the second location is alongthe second drive screw; measure a first force applied to the pipettorhead by a plurality of pipette tips in response to a first insertionforce applied the first drive screw, wherein the first force is unevenlydistributed; calculate a first torque and a second torque based upon aset of parameters including the first force, the first position, and thesecond position; and apply the first torque to the first drive screw andthe second torque to the second drive screw to counteract the unevendistribution of the first force.
 8. The motion system of claim 7,wherein the second drive screw is parallel to the first drive screw. 9.The motion system of claim 7, further comprising a first force sensorconfigured to detect the first insertion force from the first drivescrew, and a second force sensor configured to detect a second insertionforce from the second drive screw.
 10. The motion system of claim 7,wherein the first position sensor includes a first linear encoder, andthe second position sensor includes a second linear encoder.
 11. Themotion system of claim 7, further comprising a motor operatively coupledto the first drive screw, wherein the first force sensor comprises awinding of the motor.
 12. A pipette workstation comprising: a deckconfigured to support a plurality of pipette tips; a first drive screw;a second drive screw; a pipettor head engaged to the first drive screwand the second drive screw, the pipettor head disposed above the deckand movable with respect to the deck in response to a first torqueapplied to the first drive screw and a second torque applied to thesecond drive screw; a first force sensor coupled to the first drivescrew and configured to detect a first insertion force; and a controllerconfigured to: move the pipettor head to engage using the first andsecond drive screw; measure a first position of the pipettor head at afirst location using a first position sensor and a second position ofthe pipettor head at a second location using a second position sensor,wherein the first location is along the first drive screw and the secondlocation is along the second drive screw; measure a first force appliedto the pipettor head by a plurality of pipette tips in response to thefirst insertion force applied by the first drive screw, wherein thefirst force is unevenly distributed; calculate the first torque and thesecond torque based upon a set of parameters including the first force,the first position, and the second position; and apply the first torqueto the first drive screw and the second torque to the second drive screwto counteract the uneven distribution of the first force.
 13. Thepipette workstation of claim 12, wherein the controller is furtherconfigured to adjust the first torque of the first drive screw inresponse to the detected first insertion force.
 14. The pipetteworkstation of claim 13, further wherein the first position sensor is afirst linear encoder and the second position sensor is a second linearencoder offset from the first linear encoder, the first linear encoderconfigured to measure the first position of the pipettor head and thesecond linear encoder configured to measure the second position of thepipettor head, wherein the controller is further configured to adjustthe second torque of the second drive screw in response to the firstposition and the second position.
 15. The pipette workstation of claim12, further comprising a second force sensor coupled to the second drivescrew and configured to detect a second insertion force.
 16. The pipetteworkstation of claim 12, wherein the controller is further configured toapply a torque to the first drive screw to produce a predetermined firstinsertion force.
 17. The pipette workstation of claim 12, wherein thecontroller is configured to apply a torque to the second drive screw tomaintain the measured second position level with the measured firstposition.
 18. The pipette workstation of claim 12, wherein thecontroller is further configured to apply a torque to the second drivescrew to produce a predetermined second insertion force.
 19. The pipetteworkstation of claim 12, wherein the pipettor head is subdivided into afirst area and a diagonally opposed second area by a centerline and amidline, the centerline intersecting the centers of the first drivescrew and the second drive screw and the midline perpendicular to thecenterline through the midpoint of the centerline, and wherein the firstposition is measured in the first area and the second position ismeasured in the second area.
 20. The pipette workstation of claim 12,wherein the pipettor head includes a plurality of mandrels eachconfigured to engage a pipette tip, and wherein, when the plurality ofmandrels engage the plurality of pipette tips, fewer than all of theplurality of mandrels are engaged.